TETANUS. 231 



in infectious earth and in pus from a case of tetanus and 

 grown in pure culture. 



The tetanus-bacillus is a long, slender rod, from 0.3 to 0.5 p. 

 thick and from 3 to 5 n long, with rounded extremities and with 

 feeble, but distinct, motility, which, however, ceases immediately 

 in the presence of oxygen. It frequently grows in filaments, 

 the individual elements of which are not always distinctly dif- 

 ferentiable from one another. The temperature-optimum is 

 from 36 C. (96.8 F.) to 38 C. (100.4 F-) although the 

 bacillus thrives also at room-temperature. It does not develop 



Fig. 53. Bacillus tetani; X 1000 (Friinkel and Pfeiffer). 



below a temperature of 14 C. (57.2 F.), while at 42 C. 

 (^107.6 F.) or 43 C. (109.4 F.) it presents distinct invo- 

 lution-forms, and at 60 C. (140 F. ) it is destroyed quite 

 rapidly. The tetanus-bacillus is . an, anaerobic organism, 

 although it still grows in the presence of small amounts of 

 oxygen. Protected from air and light the tetanus-spores retain 

 their vitality and their virulence in cultures after the lapse of a 

 year. 



Spore-formation. At a temperature of 37 C. (98.6 F.) 

 after the lapse of thirty hours, and at room-temperature within a 

 week, the tetanus-bacillus forms spherical spores always situated 

 at one extremity. The bacillus swells at one extremity like a 

 drumstick, and there results the characteristic head-bearing 

 bacillus (pin-shaped or note-shaped). The organism is always 



